A theoretical study of the ?- and HO?-assisted propen-2-ol tautomerizations: Reactive systems to evaluate collision efficiency definitions on chemically activated reactions using SS-QRRK theory

In combustion, enols can undergo keto-enol tautomerizations, which are intermediate steps in the formation of pollutant species. this work, we performed a theoretical kinetic study step-wise propen-2-ol tautomerization catalyzed by hydrogen and hydroperoxyl radicals. Ab initio calculations at CCSD(T)/aug-cc-pVTZ//M06-2X/cc-pVTZ level were run, rate constants calculated using multistructural torsional variational transition state theory with small-curvature tunneling corrections. Hydrogen radicals induce mechanism toward keto lower barrier than that unimolecular tautomerization. The potential energy surface comprising these reactions is complex, involving different intermediates connected types pathways. hydrogen-assisted consists two where an radical takes place as result addition atom to double bond propen-2-ol. high-pressure limit acetone exhibit Arrhenius behavior, agreement previous works. hydroperoxyl-assisted tautomerization, has routes overall four steps. route highest becomes prominent above 800 K due anharmonicity effects, must be included for accurate description titled reactions. Calculations pressure-dependent showed original system-specific quantum Rice-Ramsperger-Kassel theory, together modified strong collision model (SS-QRRK/MSC), significantly underpredict bimolecular stabilization 1200 factors up three orders magnitude when compared benchmark Rice-Ramsperger-Kassel-Markus/master equation method. To solve problem, tested alternative definitions efficiency parameter improved implementation SS-QRRK/MSC approach developed us chemically activated One definitions, provided Gilbert et al. (1983), corrected constant behavior yielded maximum deviation factor only 4.5 2000 100 atm. For pressure effects negligible because energized adduct cannot compete reaction leading final product most physical conditions studied. Our used perform more modeling alcohols. Besides, SS-QRRK (1983) proposed work useful computing reactions, including all possible refinements (multi-dimensional tunneling, anharmonicity, etc.) considered calculations.